In many industries, it is desirable to deposit films onto surfaces of a substrate to provide desired characteristics to the finished coated product. For example, in the glass industry, it is often desirable to deposit films to provide characteristics to the glass related to transmittance, emissivity, reflectivity, durability, color, photocatalysis and chemical resistance.
One deposition method used to deposit films onto substrates is a sputtering method. During sputtering, a substrate is positioned within a vacuum chamber containing a rotating cylindrical target or planar target that has sputterable target material on its outer surface. An electrical field is created between the target (which acts as a cathode) and an anode in the vacuum chamber. Next, an argon gas is introduced to the vacuum chamber. Electrons in the electrical field ionize the gas atoms and create charged plasma. Sputtering occurs when plasma particles impinge on the surface of the target causing emission of sputterable target material onto a substrate.
Certain sputtering systems include magnets that create a magnetic field. Sputtering systems including magnets are often referred to as magnetron sputtering systems. The magnetic field confines the plasma within a relatively narrowly defined area along a target surface. Typically, magnets are placed behind or within the target and are arranged so that the plasma is confined at the bottom surface of the planar or cylindrical target, facing a substrate being coated directly beneath. The plasma sputters target material from this bottom surface, thereby forming a sputtering zone on the target.
In many cases, the magnets are arranged such that a sputtering zone is formed on the target surface. A problem with many previous sputtering systems is that plasma confined at certain areas tends to be denser than plasma confined at other areas. The denser the plasma, the higher the sputtering rate is of target material confined by the plasma. Thus, certain areas have denser plasma than other areas, the target material is sputtered at different rates. As a result, the target is sputtered in an uneven fashion such that the deposited film is non-uniform.
It would be desirable to provide sputtering apparatuses, systems and methods that sputter target material to deposit films having a more uniform thickness. It would also be desirable to provide sputtering apparatuses, systems and methods that provide a more uniform sputtering rate along the entire sputtering zone.